Stripping the XML from an item property.. fn-XmlDecode doesn't see to work

Hi

I'm pretty new to Nintex so hopefully this is obvious. I want to build a string from a couple of items in my list and then put that string into another item

In a "Build String" action I've put this...

{Common:InitiatorsDisplayName} :({fn-XmlDecode({ItemProperty:Detail})ItemProperty:Detail})

but this is produced...

Sam S : <div class="ExternalClass790246161DBE4B53AB550BE547366F36"><p>​Again... can we see the  title?</p></div>

I get the same thing without the {fn-XmlDecode.....

I just want the "plain" text.

Any suggestions?

Thanks

Samo